1. Field of the Invention
The invention relates to a multi-edged rotary tool with individual adjustment in a radial direction of each cutting tip or with central adjustment for all the cutting tips together.
2. Description of the Prior Art
DE 198 27 778 A1 discloses a rotary tool in which a cutting tip can be radially adjusted in a sensitive manner on a parallel spring by means of an adjusting screw without a stick-slip effect.
The tool is conceived as a single cutter; a plurality of cutting tips may be arranged one behind the other on a carrier. It can be used in particular for small bores.
Such a tool constitutes a unit of small construction. Its dimensions can be selected in such a way that it is also suitable for small bore hole diameters. In this case, axial adjustability can also be readily achieved, as is often necessary in order to produce, for example, stepped bores. For all that, however, the tool is distinguished by especially advantageous adjustability in the radial direction without another variable, in particular the setting angle, causing undesirable effects in the process. This is achieved in one embodiment by the holder being designed as a parallel bending spring arrangement. This refers to a configuration in which the head part of the holder, i.e. the part carrying the cutting tip, essentially experiences a displacement parallel to itself using elastic bending of parts of the holder.
The design can be made in such a way that the holder is essentially without load in the deflected state, and an elastic restoring force which counteracts a deflection only occurs when the adjusting device is actuated from a zero or initial position. In an especially advantageous manner, however, the holder is already held under prestress in the nondeflected state, so that freedom from play is ensured from the outset. This can be achieved by the holder forming a spring being firmly screwed to the parent body and by bearing directly against the adjusting screw in the process.
There are various possible embodiments for the aperture provided for this parallel spring design, namely those having a recess in the corner regions, which prevent notch stresses. In a very favorable embodiment, the aperture essentially has the shape of a U with a central fastening tongue.
The adjusting device is designed as a screw which engages in a thread of the parent part and is supported on the parent part. In an especially expedient embodiment, the adjusting screw together with the holder has such a wedge-surface pair that no self-locking can occur. As a result, the wedge surfaces can slide when the screw is turned in the release direction as a result of the high prestress, i.e. the holder always stays in contact with the screw.
The wedge-surface pair between holder and adjusting screw can be produced, for example, by a convex or conical section of the screw, paired with a vertical section of the holder, or also vice versa, or by mixed forms. The important factors are the direct contact of the elements and their effective direction relative to one another.
With such an adjusting device, it is possible to deflect the cutting tip radially to a finer degree than 3 μm and to produce correspondingly accurate bores. The repetitive accuracy is so precise that the movement of the adjusting screw at an annular scale arranged thereon relative to a reference point on the parent body can be assigned to a corresponding radial adjustment of the cutting tip. A circular measure of 1 mm at the screw corresponds, for example, to 1/1000 mm at the cutting tip. This repetitive accuracy is a prerequisite for maintaining quality conditions required by DIN/ISO 9000 ff.
The use of such a design for other boring purposes is not disclosed; in particular bore diameters of about 10 to 50 mm are to be realized.